B-spline Surface with Control Points:
Figure illustrated a B-spline surface defined by 6 rows and 6 columns of control points.
Figure: B-spline Surface with 6 × 6 Control Points
The knot vector & the degree in the u-direction are following
U = {0, 0, 0, 0.25, 0.5, 0.75, 1, 1, 1} and 2.
The knot vector & the degree in the v-direction are following
V = {0, 0, 0, 0, 0.33, 0.66, 1, 1, 1, 1} and 3.